孔隙填充型能源土的宏微观力学特性真三轴试验离散元分析

天然气水合物沉积物因其作为绿色新型能源且具有广阔的开发前景而备受全球瞩目。水合物在水合物沉积物（俗称能源土试样）中有不同的赋存型式，如孔隙填充型和胶结型等。针对孔隙填充型水合物的赋存形态，生成特定饱和度的能源土试样。开展了同一 平面上不同中主应力系数（b = 0、0.25、0.50、0.75、1.00）的真三轴排水试验的三维离散元模拟，将微观参数接触组构及剪切滑移率的演化规律与材料的宏观力学响应相结合，分析了中主应力对孔隙填充型能源土的宏微观力学响应的影响。结果表明：强接触处组构张量的大、中、小主值随b的变化规律与大、中、小主应力及大、中、小主应变随b的变化规律表现出良好的相关性。三向应力状态下的破坏强度接近Lade-Duncan破坏准则。能源土试样剪切滑移率随着中主应力系数的增大而增大；当处于三轴拉伸状态时，试样的剪切滑移率最大。

Macro-micro mechanical property of pore-filling type methane hydrate-bearing sediment in true triaxial tests based on distinct element analysis

Natural gas hydrate deposits, as a new type of green energy, have attracted global attention for broadly commercial exploitable prospect. Methane hydrate (MH) has different formations in the pore of methane hydrate-bearing sediment (MHBS), i.e. pore-filling, cementation, and so on. A pore-filling type MHBS with a specific MH saturation is firstly generated based on the hydrate morphology. Subsequently, a series of consolidated-drained true triaxial tests with a constant mean effective stress is carried out using the distinct element method (DEM) under the same π-plane with different intermediate stress ratios (i.e., b = 0, 0.25, 0.50, 0.75, 1.00). The influence of intermediate principal stress on the macro-micro mechanical properties of MHBS is analyzed by linking the evolution of micro-mechanical parameters (i.e. the contact fabric and the percentage of sliding contact) to the macro-scale behavior of granular material. The results show that there is a good correlation between the strong fabric changes (i.e. major, intermediate, and minor principal fabrics) and the variations in principal stresses (i.e. major, intermediate and minor principal stresses) and principal strains (i.e. major, intermediate, and minor principal strains). The three-dimensional strength of MHBS can be approximately described by Lade-Duncan failure criterion. The percentage of sliding contact increases with increasing intermediate principal stress ratio and reaches the maximum when MHBS is in the triaxial extension state.